The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, PR China.
Gene. 2013 Sep 15;527(1):82-8. doi: 10.1016/j.gene.2013.05.037. Epub 2013 Jun 7.
Cytochrome P450c17-II (cyp17-II, 17α-hydroxylase) is responsible for the production of steroid hormones during oocyte maturation in vertebrates. The comparative expression pattern of cyp17-II gene during the gonadal development stages will provide important insights into its function of gonadal development. In addition, epigenetic modification especially DNA methylation plays a vital role in regulation of gene expression. The adult female Japanese flounder at different ovarian development stage (from stages II to V) was obtained in this experiment. The expression of cyp17-II gene in the ovary of Japanese flounder during the gonadal development stages was measured by quantitative PCR. Reproductive traits included gonadosomatic index (GSI), plasma estradiol-17β (E2) and testosterone (T) were also measured. Moreover, whole CpG dinucleotides methylation status of the two CpG rich regions in cyp17-II coding region was detected by bisulfate sequencing. In the ovary, the cyp17-II gene had the lowest mRNA expression at the early ovarian development stage, but then increased afterward. The variation trends of T and E2 level were consistent with the cyp17-II expression pattern in ovary. In contrast, the whole methylation levels of each CpG rich region (exon 4 and 6) in cyp17-II coding region were declined from stages II to IV, then increased at stage V. The methylation levels of whole CpG sites in each CpG rich region were inversely correlated with the values of ovarian cyp17-II gene expression, T and E2 level, and GSI. Based on the present study, we proposed that cyp17-II may regulate the level of steroid hormone, and then stimulate the oocyte growth and maturation. The cyp17-II gene transcriptional activity was possibly affected by the methylation level of CpG rich regions in coding region. These findings will help in the study of the molecular mechanism of fish reproduction and endocrine physiology.
细胞色素 P450c17-II（cyp17-II，17α-羟化酶）负责脊椎动物卵母细胞成熟过程中类固醇激素的产生。cyp17-II 基因在性腺发育阶段的比较表达模式将为其性腺发育功能提供重要的见解。此外，表观遗传修饰，特别是 DNA 甲基化，在基因表达调控中起着至关重要的作用。本实验获得了处于不同卵巢发育阶段（从 II 期到 V 期）的成年雌性牙鲆。通过定量 PCR 测量了牙鲆性腺发育过程中卵巢中 cyp17-II 基因的表达。生殖特征包括性腺指数（GSI）、血浆雌二醇-17β（E2）和睾酮（T）也进行了测量。此外，通过亚硫酸氢盐测序检测了 cyp17-II 编码区两个富含 CpG 二核苷酸的富含 CpG 区的全 CpG 二核苷酸甲基化状态。在卵巢中，cyp17-II 基因在早期卵巢发育阶段的 mRNA 表达最低，但随后增加。T 和 E2 水平的变化趋势与卵巢中 cyp17-II 的表达模式一致。相反，cyp17-II 编码区两个富含 CpG 区（外显子 4 和 6）的全甲基化水平从 II 期到 IV 期下降，然后在 V 期增加。每个富含 CpG 区的全 CpG 位点的甲基化水平与卵巢 cyp17-II 基因表达、T 和 E2 水平以及 GSI 值呈负相关。基于本研究，我们提出 cyp17-II 可能调节类固醇激素水平，从而刺激卵母细胞生长和成熟。cyp17-II 基因的转录活性可能受到编码区富含 CpG 区的甲基化水平的影响。这些发现将有助于鱼类生殖和内分泌生理学的分子机制研究。
